AVS 59th Annual International Symposium and Exhibition
    Graphene and Related Materials Focus Topic Monday Sessions
       Session GR+EM+NS+PS+SS+TF-MoM

Paper GR+EM+NS+PS+SS+TF-MoM1
Synthesis Ingredients Enabling Low Noise Epitaxial Graphene Applications

Monday, October 29, 2012, 8:20 am, Room 13

Session: Graphene Growth
Presenter: D.K. Gaskill, U.S. Naval Research Lab
Authors: D.K. Gaskill, U.S. Naval Research Lab
L.O. Nyakiti, U.S. Naval Research Lab
V.D. Wheeler, U.S. Naval Research Lab
A. Nath, George Mason Univ.
V.K. Nagareddy, Newcastle University, UK
R.L. Myers-Ward, U.S. Naval Research Lab
N.Y. Garces, U.S. Naval Research Lab
S.C. Hernández, U.S. Naval Research Lab
S.G. Walton, U.S. Naval Research Lab
M.V. Rao, George Mason Univ.
A.B. Horsfall, Newcastle Univ., UK
C.R. Eddy, Jr., U.S. Naval Research Lab
J.S. Moon, HRL Labs LLC
Correspondent: Click to Email
Sensors made from graphene flakes have demonstrated single molecule detection [Schedin et al., Nat Mat 6, 652 (2007) ]; this ultra-sensitivity is likely due to the high crystalline quality of the graphene and the associated relative lack of defects that give rise to noise. The low noise nature of high quality graphene should also facilitate other applications, e.g., low-noise amplifiers. Combined with the unique ambipolar property of graphene field effect transistors (FETs), the low noise charac­ter of graphene would significantly advance the performance of frequency multipliers, mix­ers and high-speed radiometers. To exploit these applications, high qual­ity, reproducible wafer-scale epitaxial graphene (EG) with minimal thickness varia­tions and defects are essential requirements. Here, crucial graphene synthesis elements required to achieve the wafer-scale quality goal are described. Understanding the effect of substrate misorientation as well as hydrogen etch and Si sublimation conditions for graphene syn­thesis on the (0001) SiC surface is essential to achieve improved and reproducible wafer-scale graphene quality. For example, the impact of processing factors such as temperature con­trol, laminar gas flow and substrate rotation on large area EG uniformity are described using examples created in an Aixtron SiC epitaxy reactor. In addi­tion, managing SiC step formation on the nominal (0001) orientation is significant for achieving uniform EG thickness on terraces and to minimize additional growth at the step edges; this is illustrated using data from atomic force microscopy and scan­ning electron microscopy images in combination with Raman spectroscopy maps and x-ray photoelectron spectroscopy analysis. Managing step formation combined with optimal growth leads to the suppression of the Raman defect “D” band confirming mini­mal grain boundaries and defects, which are additional sources of electronic noise. Lastly, contactless Lehighton resistivity maps of 75 mm wafers are used to illustrate the over­all uniformity of optimally synthesized graphene as well as to show the re­sistance state-of-the-art, with individual wafers exhibiting about a ±3% relative variation. Examples of the impact of this synthesis approach on chemical sensors devices and FETs will be shown, each exhibiting 1/f noise behavior down to 1 Hz and possessing noise spectral densities similar to reports from exfoliated graphene. Hence, careful control of EG formation across the wafer results in improved quality which subsequently leads to the reduction or elimination of additional noise sources from graphene defects that would then adversely affect device performance.